Spark gap for x-ray apparatus



Dec. 17, 1935.

H. G. FISCHER ET AL SPARK GAP FOR X-RAY APPARATUS Filed Dec. 7, 1933 Patented Dec. 17, 1935 UNITED STATES PATENT OFFICE SPARK GAP FOR X-RAY APPARATUS Herman G. Fischer, Peter P. Musket, and Howard H. Osborn, Chicago, 111., assignors to H. G. Fischer Co. Inc., Chicago, 111., a corporation of Illinois Application December 7, 1933, Serial No. 701,302 1 Claim. (Cl. 250-34) This invention relates to X-ray machines and as synthetic resin, phenol condensate, or the like, has more particular reference to improvements and are suitably held in position on the base 20. in spark gap mountings for such apparatus. These posts are provided with axial bores to re- A principal object of the present invention is ceive the high potential leads l2 and I3 extend- 5 the provision of spark gaps which will prevent ing therethrough. The electrodes [6 and I1, 5 shock to the flexible insulated cables, or exceS- which constitute the outer electrodes or high sive strain thereon. potential electrodes of the spark gap, have the Another object of the invention is to safeguard form of metal spheres, each sphere being sethe leads against sudden, excessive voltage surges cured to a short threaded stud 23 and 24, re-

10 which occur in high voltage operations. spectively. 10

A further object of the invention is the pro- The cylindrical posts 2| and 22 are each provision of a spark gap across the high voltage vided adjacent the top with a radial tapped hole, leads of X y apparatus, wh r n he p ing of adapted to receive the threaded stud of the rethe several electrodes is adjustable. spective sphere, so that upon proper insertion Another important object of the invention is of the threaded stud into the respective tapped 15 the provision of spherical spark gap electrodes bore, the stud will be moved into conductive conlocatcd at the corners of a triangle with two of tact with the respective lead I2 and I3 to conthese electrodes at the ends of the base of the ne'ct the respective sphere conductively with the triangle while the grounded intermediate elec said lead.

trode is located in the apex of the triangle an The tapped bores in the two posts 2| and 22 20 equal distance from the other two electrodes. are positioned an equal distance from the surface Numerous other objects and advantages of the of the base 29 and are arranged within said invention will be apparent from the following posts in such manner that the radial lines exdescription, which, when taken in connection tending from the centers of the electrodes [6, ll

with the accompanying drawing, discloses a preaxially through the studs 23, 24 form, on ,each of 25 ferred embodiment thereof. the mountings, an equal angle with a line con- On the drawing, necting the axes of the posts 2|, 22. Figure 1 shows, diagrammatically, the relation The central electrode of the spark gap is 10- of the spark gap to an X-ray tube; cated at a greater distance from this connecting Fig. 2 is a side elevation of the electrodes of line, preferably in such manner that extensions 30 the spark gap and their mountings; and of the radial lines through the spheres l6 and I! Fig. 3 is a top view of the spark gap. will intersect each other in the center of the Referring to the d aw g. reference character third electrode l8 which is grounded. The three It indicates an X-ray tube. Two electrodes conelectrodes, therefore, may be described as being nect this tube with high potential flexible inmounted in triangular relation with the two out- 35 sulated leads l2 and I3. The X-ray tube is wired or electrodes located at the ends of the base of in the u ua W 3, using the high tension l ds an isosceles triangle at the apex of which the and 23 connected to the cathode and anode, recentral electrode is mounted. spcctiv'ely, and a subsidiary source of electric This third or grounded electrode 18 also is 40 energy M for heating the cathode. provided with a threaded stud 25 which extends 40 A spark gap Sy indicated at 5, is shunted diametrically through a tapped passage in the across the high voltage leads I2 and 13. This post 26 of the spark gap mounting, whereby spark gap system comprises two electrodes I6 saidelectrode I8 may be spaced different disand 5'] whic a conductively connected with tances from the said connecting line, or base of the voltage leads l2 and I3, respectively, the triangle. A nut 2'! is adapted to maintain 45 and a third electrode 18 which is grounded. the stud 25 and third electrode la in adjusted Upon surges of electric energy arising in the position relative to its post 26 and to the other high voltage circuit, discharge will occur between electrodes of the spark gap. either one of the electrodes I6 and Il and the The electrodes I6, I1, l8 of the spark gap grounded electrode of the spark gap, thus avoidare directed toward each other solely with their 50 ing injury to the high tension leads. spherical surfaces and are so spaced that the In the embodiment of the invention illustrated discharge of the spark from one outer electrode in the drawing, the spark gap is supported by a to the other outer electrode, while skipping the base plate 2 carrying two posts 2|, 22 which central. or grounded electrode, cannot occur. are or may be made of insulating material, such t is thought that the invention and many of 55 its attendant advantages will be understood from the foregoing description, and it will be apparent that various changes may be made in the form, construction and arrangement of the parts Without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the form hereinbefore described being merely a preferred embodiment thereof.

We claim:

A spark gap arrangement for X-ray tubes, comprising a base, posts carrying the leads for the X-ray tube mounted on said base, electrodes fixedly secured to said posts, studs interposed between the surface of the electrodes directed towards said posts and the leads within said posts, a third post rising from the base, and a grounded electrode secured to said third post out of salinement with said first mentioned electrodes and 5 spaced equally therefrom, said grounded electrode being adjustable on a line extending at right angles to a line intersecting said first mentioned electrodes.

HERMAN G. FISCHER. PETER P. MUSKET. HOWARD I-I. OSBORN. 

